Packed bed

Under a fixed-bed reactor is defined as a special type of reactor in which one or more fluids flow through a fixed bed or packing. The fixed bed often serves the fixation of heterogeneous catalysts or - in bioreactors - the microorganisms. The chemical or biological catalyst can be present or even of such porous media in the form of coated surface but solid body (including cylinder and complex geometries often but balls ).

Fixed-bed reactors can be traversed by the fluids both from above and from below, and in the opposite direction. Especially in the case of a liquid and a gaseous phase is referred to as trickle tablets or trickle bed reactors, if the liquid phase flows through the reactor from top to bottom, and the gas is the continuous phase and the packed bubble column, if the gas from below passes through the package to the top and the liquid phase is continuous. Other material flow combinations are the exception in the industry.

The main advantage of the fixed bed reactor with respect to reactors with dissolved catalyst is that the catalyst must not be separated from the product and thus account for a filtration step.

The main disadvantages compared to reactors with dissolved catalyst are that additional resistances occur particularly in the mass transfer and heat transport.